Understanding Meningitis -- the Basics

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What Is Meningitis?

Meningitis is a relatively rare infection that affects the delicate membranes -- called meninges (men-in'-jeez) -- that cover the brain and spinal cord. Bacterial meningitis can be deadly and contagious among people in close contact.

Viral meningitis tends to be less severe and most people recover completely without specific therapy.

Fungal meningitis is a rare form of meningitis and generally occurs only in people with weakened immune systems.

What Causes Meningitis?

Meningitis is almost always caused by a bacterial or viral infection that began elsewhere in the body, such as in the ears, sinuses, or upper respiratory tract. Less common causes of meningitis include fungal infection, autoimmune disorders, and medications.

Bacterial Meningitis

Bacterial meningitis is an extremely serious illness that requires immediate medical care. If not treated quickly, it can lead to death within hours -- or lead to permanent damage to the brain and other parts of the body.

Bacterial meningitis is caused by any one of several bacteria. The most common bacteria causing meningitis in children and adults in the U.S. are Neisseria meningitidis ("meningococcus"), Streptococcuspneumoniae ("pneumococcus") and, in older patients with decreased immunity, Listeria monocytogenes. Haemophilus influenzae type b (Hib) was a common cause of meningitis in infants and young children until the Hib vaccine was introduced for infants. Vaccines are available for both Neisseria meningitidis and Streptococcus pneumoniae. They're recommended for all children and adults at special risk.

The bacteria can spread from person to person through coughing and sneezing. If you are around someone who has bacterial meningitis, contact your health care provider to ask what steps you need to take to avoid infection.

In many instances, bacterial meningitis develops when bacteria get into the bloodstream from the sinuses, ears, or other part of the upper respiratory tract. The bacteria then travel through the bloodstream to the brain.

Viral Meningitis

Viral meningitis is more common than the bacterial form and generally -- but not always -- less serious. It can be triggered by a number of viruses, including several that can cause diarrhea.

People with viral meningitis are much less likely to have permanent brain damage after the infection resolves. Most will recover completely.